Project Summary Chronic beryllium disease (CBD) results from beryllium (Be) exposure in the workplace and is characterized by granulomatous inflammation and the accumulation of Be-specific, Th1-type cytokine-secreting CD4+ T cells in the lung. Be exposure is also associated with the induction of cytokine/chemokine secretion and the coordinated recruitment of innate and other adaptive cells to the lung. Our preliminary data show that exposure of HLA-DP2 Tg mice to Be oxide (BeO) as well as stimulation of bronchoalveolar lavage (BAL) cells derived from CBD patients with BeSO4 both induced significant CCL3 and CCL4 secretion. Importantly, we have identified related peptides derived from CCL3 and CCL4 that are recognized as Be-dependent neoantigens by TCRs expressed on CD4+ T cells derived from the BAL of HLA-DP2-expressing CBD patients. Be-loaded HLA-DP2-CCL3 and HLA-DP2-CCL4 tetramer staining showed that these ligands were recognized by 10-40% of IFN-?-expressing, Be-specific CD4+ T cells in the BAL, supporting the importance of these T cells in the Be-induced immune response. Collectively, our data demonstrate that innate mediators, CCL3 and CCL4, are secreted into the lung in response to Be while also being targeted as key T cell epitopes recognized by a large fraction of Be-specific CD4+ T cells. Thus, in the setting of persistent antigen exposure, we hypothesize that Be-induced CCL3 and CCL4 secretion creates a destructive cycle of innate and adaptive immune activation and that depletion of these epitope-specific CD4+ T cells with genetically-engineered T cells will modulate Be-induced lung inflammation. Using HLA-DP2 Tg mice, Aim 1 will determine the cellular source and role of BeO-induced CCL3 and CCL4 secretion as innate mediators of lung inflammation while Aim 2 will track the dynamics of CCL3/Be- and CCL4/Be-specific CD4+ T cells in a murine model of CBD. The final aim will utilize chimeric antigen receptor (CAR) T cells to target epitope-specific CD4+ T cells in HLA-DP2-expressing mice and CBD patients as a potential therapeutic approach in the treatment of Be-induced disease. The significance of the proposed study rests on the novel identification of chemokines involved not only in innate inflammatory cell recruitment, but also encoding Be-modified self-peptides that bind to HLA-DP2 and represent dominant T cell epitopes in CBD. The successful completion of these studies using innovative technology to deplete epitope-specific T cells in HLA- DP2-expressing mice and humans with Be-mediated disease will lead to the potential use of CAR T cells as a therapeutic option for CBD, a disease with few alternatives to systemic corticosteroids.